Clauses can be divided into two kinds: dependent and independent. A dependent clause contains a subject and verb, but cannot stand on its own as a complete sentence; an independent clause includes a subject and a verb, and expresses a complete thought. An independent clause is a complete sentence in itself but may appear together with other clauses in compound or complex sentences. For example, "as soon as you get here" is a clause; it has a subject (you) and a verb (get), but it doesn't express a complete thought. Therefore it is not independent; it can't stand alone as a sentence.
On the other hand, "we will go out together" is an independent clause with a subject and verb, and it can stand on its own as a sentence. When joined together, as in "As soon as you get here, we will go out together," the phrase and clause create a sentence comprising an independent and dependent clause.
Another way to recognize dependent and independent clauses is to look for signal words. Signal words often appear before phrases and, once you're in the habit of looking for them, can alert you to a dependent clause. For example, the phrase "When it rains in Seattle," is a dependent clause. It has a subject ("it") and a verb ("rains"), but it does not express a complete thought. The word "When" is also another indicator that you are looking at a phrase. "When" is one of several signal words called a subordinating conjunction. Other subordinating conjunctions include: although, because, before, how, if, since, though, where, whether, and while.
You can use a comma to join dependent and independent clauses. The comma indicates where one clause ends and another begins. In some cases, you won't need a comma if there is no confusion about the boundary of the clauses. Here are some examples:
The use of a comma when a dependent clause comes before an independent clause (as in Example 1 above) is optional, particularly when joining two short clauses, but you'll most commonly see a comma used to separate the two clauses. However, that guideline is generally not applied when the sequence of phrases is reversed, as in Example 3.
You have two choices when joining sentences—or two independent clauses.
Suppose you want to join the following sentences:
Joining sentences 1 and 2 together using the strategies outlined above, produces two possible options:
In Example 3a, the writer uses the conjunction "and" with a comma and in 3b, a semicolon.
Each has a
slightly different rhetorical effect. With "and," the relationship between the oil and the antioxidant substances is explicit. In other words, the ideas have been combined in a way that makes it clear to the reader what the relationship is between the first and the second
clauses.
The semicolon, on the other hand, is no less appropriate, but the reader has to judge from the context what
the relationship is between the ideas expressed in each clause since a semicolon can suggest several things, from combination and contrast to simply giving additional information. For example:
Here a semicolon joins two sentences that express contrast between two people's preferences. This relationship between clauses could be made even more explicit, however:
In most cases, joining two independent clauses (i.e., clauses that can stand alone as complete sentences) by a comma creates a comma splice.
In this example, the two ideas expressed are clearly related, as the author wishes to contrast the characters' dialogue with the narrator's. However, the sentence contains a comma splice because the clauses on both sides of the comma are independent clauses:
In other words, the two sentences above can stand alone as complete sentences. Joining them with a comma results in a comma splice.
To correct a comma splice, take a look at the clauses that make up the sentence. Be sure that each sentence includes only one independent clause and the rest dependent clauses.
A dependent clause cannot stand alone as a sentence. Like an independent clause, it has a subject and a verb. It may not, however, express a complete thought and may begin with a signal word called a subordinating conjunction. The chart below outlines common coordinating and subordinating conjunctions discussed in this section.
| Common Coordinating Conjunctions | Common Subordinating Conjunctions |
|
and but for nor or so yet |
although because before how if since though when where whether while |
Using the chart above, we can correct the comma splice from the previous sentence in several ways:
| Option for correcting comma splice | Corrected sentence or sentences |
| Continue to use a comma to link the two portions of the sentence but turn one independent clause into a dependent clause with a coordinating conjunction | The dialogues between Clarence and Mariano advance the novel's plot, but the narrator's interventions, on the other hand, are extraneous. |
| Continue to use a comma to link the two portions of the sentence but turn one independent clause into a dependent clause with a subordinating conjunction | While the dialogues between Clarence and Mariano advance the novel's plot, the narrator's interventions, on the other hand, are extraneous. |
| Make the two independent clauses into separate sentences | The dialogues between Clarence and Mariano advance the novel's plot. The narrator's interventions, on the other hand, are extraneous. |
| Use a semi-colon to link two independent clauses | The dialogues between Clarence and Mariano advance the novel's plot; the narrator's interventions, on the other hand, are extraneous. |
A final problem related to sentence structure concerns sentence fragments. Sentence fragments occur when a writer punctuates a phrase as if it could stand alone as a sentence, for example:
"Because everyone is bound by it" is not a complete sentence, but a dependent clause. To correct the fragment, you could join the dependent clause to the independent clause (or the main clause). For example:
The best way to test whether or not you have a sentence fragment is to evaluate whether the clause expresses a complete thought. If not, then look for signal words that could indicate the beginning of a dependent clause. If you have a clause that does not express a complete thought and begins with a signal phrase, then you're likely looking at a sentence fragment.
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